For the Long Term Evolution (LTE) system, after undergoing a plurality of releases such as Releases (R) 8/9/10, the R11 technology is to be developed successively. Currently, part of R8 products start to be gradually commercial, and R9 and R 10 products have yet to be programmed.
After undergoing the R8 stage and R9 stage, many new characteristics are added in the R10 based on the previous two stages, for example, pilot frequency characteristics such as Demodulation Reference Signal (DMRS) and Channel State Information Reference Signal (CSI-RS), transmission and feedback characteristics such as 8-antennae supporting and so on, and especially the inter-cell interference avoidance technology is considered in the enhanced Inter-Cell Interference Cancelling (eICIC) technology based on the consideration of R8/9 ICIC. With regard to the technology for solving the inter-cell interference problem, cell interference avoidance in a homogeneous network is mainly considered in the initial phase of R10 stage, wherein the eICIC technology and Coordinated Multi-point (CoMP) technology are mainly considered. As the name suggests, the CoMP means that a plurality of points coordinate to transmit data to one or more User Equipments (UE) with the same time-frequency resources or different time-frequency resources. Thus, inter-cell interference can be reduced, cell edge throughput can be improved, and cell coverage can be expanded. However, since introduction of more scenarios in a heterogeneous network, complexity of the CoMP technology and time limitation of the R10 discussion are considered in the later period of discussion, it is eventually decided that additional CoMP standardization contents are not introduced in the R10 stage, but it can be designed according to demands of the CoMP part when the CSI-RS is designed, thus the CoMP technology is not further discussed after the 60bis conference.
Configuration information of the R10 CSI-RS mainly includes Non Zero Power (NZP) CSI-RS configuration signaling and zero power CSI-RS configuration signaling. The non zero power CSI-RS configuration mainly considers to notify a terminal side of the time-frequency resource location of each non zero power CSI-RS within one subframe by means of using table indexes, as shown in Table 1 and Table 2; and to notify the terminal side of the number of time-frequency resources occupied by the non zero power CSI-RS and corresponding antenna ports and notify the terminal side of subframes receiving the CSI-RS through subframe offset and cycle indexes, as shown in Table 3.
TABLE 1Resource mappings configured by the CSI-RS in subframes with normal cyclic prefixThe number of configured CSI-RS antenna portsCSI-RS1 or 248configurations(k′, l′)ns mod 2(k′, l′)ns mod 2(k′, l′)ns mod 2Frame0(9, 5)0(9, 5)0(9, 5)0structure1(11, 2) 1(11, 2) 1(11, 2) 1types 12(9, 2)1(9, 2)1(9, 2)1and 23(7, 2)1(7, 2)1(7, 2)14(9, 5)1(9, 5)1(9, 5)15(8, 5)0(8, 5)06(10, 2) 1(10, 2) 17(8, 2)1(8, 2)18(6, 2)1(6, 2)19(8, 5)1(8, 5)110(3, 5)011(2, 5)012(5, 2)113(4, 2)114(3, 2)115(2, 2)116(1, 2)117(0, 2)118(3, 5)119(2, 5)1Only20(11, 1) 1(11, 1) 1(11, 1) 1frame21(9, 1)1(9, 1)1(9, 1)1structure22(7, 1)1(7, 1)1(7, 1)1type 223(10, 1) 1(10, 1) 124(8, 1)1(8, 1)125(6, 1)1(6, 1)126(5, 1)127(4, 1)128(3, 1)129(2, 1)130(1, 1)131(0, 1)1
TABLE 2Resource mappings configured by the CSI-RS in subframes with extended cyclic prefixThe number of configured CSI-RS antenna portsCSI-RS1 or 248configurations(k′, l′)ns mod 2(k′, l′)ns mod 2(k′, l′)ns mod 2Frame0(11, 4) 0(11, 4) 0(11, 4)0structure1(9, 4)0(9, 4)0 (9, 4)0types 12(10, 4) 1(10, 4) 1(10, 4)1and 23(9, 4)1(9, 4)1 (9, 4)14(5, 4)0(5, 4)05(3, 4)0(3, 4)06(4, 4)1(4, 4)17(3, 4)1(3, 4)18(8, 4)09(6, 4)010(2, 4)011(0, 4)012(7, 4)113(6, 4)114(1, 4)115(0, 4)1Only16(11, 1) 1(11, 1) 1(11, 1)1frame17(10, 1) 1(10, 1) 1(10, 1)1structure18(9, 1)1(9, 1)1 (9, 1)1type 219(5, 1)1(5, 1)120(4, 1)1(4, 1)121(3, 1)1(3, 1)122(8, 1)123(7, 1)124(6, 1)125(2, 1)126(1, 1)127(0, 1)1
TABLE 3CSI-RS subframe configurationCSI-RS-subframeCSI-RS cycleCSI-RS subframe offsetconfigurationTCSI-RSΔCSI-RSICSI-RS(subframe)(subframe)0-45ICSI-RS 5-1410ICSI-RS − 515-3420ICSI-RS − 1535-7440ICSI-RS − 35 75-15480ICSI-RS − 75
The zero power CSI-RS notifies the terminal side of resource elements on which rate matching is required to be performed by using a 16-bit bitmap sequence. The terminal side is notified of the subframe in which the zero power CSI-RS is located through the subframe offset and cycle, as shown in Table 3.
An object of the non zero power CSI-RS is mainly to make the terminal side measure CSI and feed it back to a base station side. A main object of the zero power CSI-RS is to reduce interference of data services with the CSI-RS so as to improve the accuracy of CSI measurement, the terminal side is informed of the resource location of the CSI-RS at the base station side, and the terminal side assumes that the base station does not place a Physical Downlink Shared Channel (PDSCH) or other reference signals or channels in the resource location of the zero power CSI-RS.
The R11 is required to consider the influence of CoMP on the standard, it is particularly required to consider configurations of interference measurement resource and resource configurations of the zero power CSI-RS. In the latest 68bis conference, it is discussed that more accurate interference estimation performance can be obtained by using the resource measurement interference of the zero power CSI-RS, and meanwhile, it also can be partly compatible with an R10 terminal, which makes the R10 terminal avoid a performance loss of the PDSCH punching resulted from the interference measurement resources by configuring the zero power CSI-RS. If the way of zero power CSI-RS measurement interference is introduced in the R11 stage, rate matching resources required to be identified by the terminal side include the following three kinds:
1. Non zero power CSI-RS resource: it mainly refers to that the base station side sends the CSI-RS in the way of 8 or 4 ports, but the terminal side can only maximally support 4 or 2 ports, thus rate matching is required to be performed in other port locations that cannot be identified at this point; or the base station side sends the CSI-RS, but the terminal side adopts feedback modes such as 1-0, 2-0 or 3-0 mode, thus it is not required to configure CSI-RS ports at the moment, and it is only required to configure the zero power CSI-RS.
2. Zero power CSI-RS resource: used for reducing the interference of data services on the CSI-RS measurement.
3. Zero power CSI-RS resource: used for the terminal side measuring interferences in corresponding resource locations.
Configuration objects of the first and second kinds of resources are identical with a configuration object of the R10 zero power CSI-RS; the third kind of resource is a newly added zero power CSI-RS used for interference measurement. Therefore, it is required to have new zero power CSI-RS configuration ways with regard to the R11, two parts are at least included, one part is used for interference measurement; and the other part is used for rate matching. For an easy description, the zero power CSI-RS used for interference measurement is temporarily called the Interference Measurement Resource (IMR), and the zero power CSI-RS used for rate matching is called the Rate Matching Resource (RMR).
Besides being required to measure channel information on the NZP CSI-RS, the R11 terminal is also required to measure interference information on the IMR, and one R11 terminal can configure a plurality of NZP CSI-RSs and IMRs, thus a concept of CSI Process is introduced in the discussion during the R11 conference, one CSI process corresponds to a channel part of one NZP CSI-RS and an interference measurement information part of one IMR. Moreover, in discussions of the eICIC of R10 and the Further eICIC (feICIC) of R11, a concept of Subframe Sets is introduced, with regard to a situation that different subframe sets respectively correspond to different interferences, for example, two subframe sets, i.e., a subframe set 0 and a subframe set 1, are configured, the subframe set 0 corresponds to a Non Almost Blank Subframe (ABS), the subframe set 1 corresponds to an ABS, and two subframe sets constitute all valid downlink subframes.